Blade servers have been widely used in various applications. A rack server system includes blade servers in a rack system for convenience of operation.
A blade server of the rack server system functions as a computer with complete functions. In other words, a blade server has peripheral devices such as a power supplier and a heat dissipation device in addition to its core components (such as CPU, motherboard, random access memory (RAM) and hard disc).
If AC-grid power is unstable, operations of the server will be unstable (such as shut-down) and data stored in the server may even be damaged. An uninterruptible power system (UPS) is used to avoid data loss and damage to electronic apparatus if power supply is abnormal, so as to effectively protect internal elements of the server and assure lifespan and accuracy of the server. However, reliability of existing UPS is still not satisfactory.
So, a battery backup unit (BBU) is in the rack server system to replace/assist the UPS for low cost, high efficiency and high stability. However, it is important how and when the BBU identifies that the AC-grid power becomes interruptible/unstable so as to timely provide power to the rack server system.
When the AC-grid power is normally supplied, an AC/DC power supplier provides power to the rack server system for charging the BBU. When the AC-grid power becomes interruptible/unstable, the AC/DC power supplier stops providing the power and notifies the BBU, so that the BBU provides power to maintain normal operations of the rack server system. Therefore, to avoid the rack server system being affected by unstableness/interruption of the AC-grid power, the change of power supply source (from the AC/DC power supplier to the BBU) shall never be interrupted.
However, the current BBU technology still has the following technology disadvantages:
Firstly, the AC/DC power supplier detects whether the AC-grid power is interruptible/unstable but the BBU does not have any AC-grid power detection circuit. When the AC-grid power becomes interruptible/unstable, the rack server system will fail if the AC/DC power supplier cannot correctly notify the BBU.
Secondly, even to include an AC-grid power detection circuit in the BBU, the detection of the AC-grid power is not easy because the AC-grid power is normally in cosine waves and the detection circuit may easily end up with erroneous detection.
Thirdly, even if the AC-grid power is not detected by the BBU and the BBU and the rack server system are directly connected in parallel, the power supplied by the BBU is usually inefficient and makes the rack server system inefficient accordingly. Besides, if power storage in the BBU is insufficient, the rack server system would fail when the AC-grid power becomes interruptible/unstable.
Therefore, the disclosure provides a rack server system and a BBU thereof for improving the shortcomings of the current technologies.